1. Field of the Invention
The invention relates to improved rapid curing, weatherable epoxy coatings.
2. Description of Other Relevant Materials in the Field
Cycloaliphatic epoxy resins prepared by the hydrogenation of glycidyl ethers of bisphenol A or other di- or polyphenols may be reacted with selective curatives to form coatings that are resistant to UV degradation. Cycloaliphatic epoxy resins are prepared by the process described in U.S. Pat. No. 3,336,241. These resins are much less reactive with conventional epoxy curatives than are the phenolic-based glycidyl ethers.
U.S. Pat. No. 4,051,195 to W. F. McWhorter teaches curable epoxy resin compositions comprising (1) a blend of an epoxide resin and a polyacrylate or polymethacrylate ester of a polyol wherein the ester contains more than one terminal acrylate or methacrylate and (2) an aliphatic polyamine curing agent. The weight ratio of epoxide resin: ester is 100:5 to 100:100. The aliphatic polyamine is incorporated into the resin composition in a specified amount. The epoxy resin compositions are said to cure rapidly even at low temperature and are useful as coatings and adhesives.
U.S. Pat. No. 4,528,345 to H. G. Waddill teaches a method for making weather-resistant epoxy coatings. The method comprises prereacting a cycloaliphatic diepoxide resin with aminoethylpiperazine or a mixture of aminoethllpiperazine and polyoxyalkylenepolyamine in an amount which is balance to give the maximum level of primary amine reaction without yielding an excessively viscous reaction product. The prereacted product is reacted with a curing amount of a polyoxyalkylene polyamine and an accelerator.
U.S. Pat. No. 4,189,564 to H. G. Waddill teaches an accelerator for curing epoxy resins. The accelerator comprises piperazine, N-aminoethylpiperzine and triethanolamine. The product comprising 65 to 80 wt % triethanolamine, 10 to 20 wt % piperazine and 5 to 1 wt % N-aminoethylpiperazine is sold commercially as Accelerator 399 by Texaco Chemical Co. The accelerator is said to be synergistic for accelerating the curing of a polyglycidyl ether of a polyhydric phenol cured with a polyoxyalkylene polyamine at ambient or elevated temperatures. Such amines include polyoxypropylene diamines of the formula: EQU NH.sub.2 CH(CH.sub.3)CH.sub.2 [OCH.sub.2 CH(CH.sub.3)].sub.x NH.sub.2
wherein x ranges from 2 to 40. Such amines also include polyoxypropylene triamines of the formula: ##STR2## wherein R is a lower alkyl and x+y+z ranges from 3 to 40.
These diamines and triamines may be synthesized according to U.S. Pat. No. 3,654,370 to E. L. Yeakey which teaches a method comprising a nickel, copper and chromium catalyst for aminating polyols.
U.S. Pat. No. 4,588,788 teaches the esterification products of a mixture of carboxylic acids of the formula EQU CH.sub.2 =CHCO.sub.2 (CHCH.sub.2 CO.sub.2).sub.n H.
This product and a mono- or polyhydric compound are used as reactive diluents for polyepoxides which are reacted with an aliphatic amine curing agent.